Project Summary Optimal functioning of the medial prefrontal cortex (mPFC) relies on synaptic connections made onto dendritic spines in pyramidal neurons. Prefrontal dysfunction resulting from chronic stress and stress-related psychiatric illnesses are each linked to decreases in dendritic spine number and shape alterations in this cortical region. Work from our laboratory and others has shown that chronic stress and elevated glucocorticoids, the end products of the hypothalamo-pituitary-adrenal stress axis activation, induce structural deficits marked by dendritic spine loss in mPFC and impaired prefrontal cognitive functions. While some progress has been made in elucidating the biochemical and genetic components underlying disrupted prefrontal plasticity in animal models of psychiatric illnesses, more work is needed to identify the cellular mechanisms accounting for these changes to help develop targets for therapeutic intervention. In this regard, recent consideration has been given to the idea that mitochondrial deficiencies may contribute to chronic stress-induced cognitive impairments and the pathogenesis of human psychiatric disorders. A-kinase anchoring protein 1 (AKAP1) is a mitochondrial scaffolding protein that recruits protein kinase A (PKA) to the outer mitochondrial membrane leading to phosphorylation and inactivation of the mitochondrial fission protein, dynamin-related protein 1 (Drp1). We have previously shown that AKAP1 increases mitochondrial membrane potential, an indicator of the cell's ability to generate ATP by oxidative phosphorylation, whereas deletion of AKAP1 leads to mitochondrial fission and dendritic spine loss in cortical neurons. These observations have culminated in the novel hypothesis that chronic stress-induced alterations in prefrontal structural and functional plasticity are mediated by diminished AKAP1 signaling in mPFC neurons. Therefore, the goal of this exploratory/developmental R21 is to examine the role of AKAP1 in chronic stress-induced dendritic spine loss and functional compromise in mPFC neurons, thus developing a data set for a future R01. In aim 1, we will interrogate whether CVS's adverse effects on prefrontal dendritic spine structure are accompanied by AKAP1 loss, Drp1 dephosphorylation/activation, and mitochondrial fragmentation. Aim 2 will use AKAP1 KO mice and lentiviral delivery of wild type and PKA-binding deficient AKAP1 to identify the signaling mechanisms accounting for disruption of prefrontal mitochondrial, dendritic spine, and behavioral alterations. The long-term goal of this line of research is to elucidate the key mechanisms linking mitochondrial dynamics to stress-related prefrontal dysfunction, as this is a common underlying feature of stress-related psychiatric disorders such as major depressive illness.